Effect of heterophil depletion by 5‐fluorouracil on infectious bronchitis virus infection in chickens

Abstract

An anti-tumour drug, 5-fluorouracil (5 FU) was used to deplete heterophils in 11-day-old white leghorn chickens. The reduction in heterophil numbers was monitored by total and differential white cell counts in the peripheral blood. Three days after injection of 5 FU, when the heterophil numbers were significantly reduced, chickens were infected with the Massachusetts strain of infectious bronchitis virus (IBV). Following infection, although the numbers of birds exhibiting clinical signs (nasal exudate) were significantly higher in the 5 FU treated group, the consistency of the nasal exudate was characteristically thin and watery. No significant differences were seen in the virus titres in trachea, lung and kidney between normal and heteropaenic chickens infected with IBV. However, the epithelial cell damage in the tracheal sections was less in the heterophil-depleted chickens.